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Place light bulbs in white cells so that every white cell is illuminated. Black cells with numbers tell you exactly how many bulbs are adjacent to them.
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About Light Up
Light Up (also called Akari) is a Nikoli puzzle where you place light bulbs in a grid of white and black cells. Each bulb illuminates the entire row and column in both directions until blocked by a black cell. Your goal: illuminate every white cell while ensuring no two bulbs shine on each other.
Black cells with numbers tell you exactly how many bulbs are adjacent to them orthogonally. Black cells without numbers impose no constraint but still block light. The puzzle is solved when every white cell is illuminated and no two bulbs are in each other’s line of sight.
Light Up has a uniquely satisfying quality: placing a bulb immediately reveals which cells it illuminates, creating visible progress with every move. The constraint that bulbs cannot see each other forces careful placement even in areas with no numbered clues. It’s a wonderful balance of local (clue-driven) and global (illumination coverage) logic.
A good strategy is to start with numbered black cells at 0 (neighbors are safe) and at maximum (all neighbors get bulbs), then trace the illumination outward to find remaining dark cells that can only be lit from one direction.
Frequently asked questions
What is Light Up?
Light Up (Akari) is a logic puzzle where you place light bulbs in white cells. Bulbs illuminate all cells in their row and column until blocked by a black cell. Every white cell must be lit, and no two bulbs may illuminate each other.